Coal mine operators are continuously seeking soluble oil concentrates which form stable emulsions with water, and more particularly soluble oil concentrates which are capable of forming stable emulsions of a minor part of concentrate and a major part of water, such as are used in roof support jacks in mines. Because of the use to which these emulsions are subjected, which in may cases involves standing static for thirty days or more in a mine roof support jack, the emulsions must have extremely good stability. Such emulsions also have utility as cutting oils for maching operations.
According to the present invention a soluble oil concentrate which forms stable emulsions with water is prepared by combining an emulsifier system with a base oil in which the emulsifier system comprises a conventional emulsifier package for soluble oils and a synergistic amount of (a) a mixture of an oxazoline derivative with straight or branched chain alcohol and fatty acid substituents and an amide with straight or branched chain alcohol and fatty acid substituents and (b) an ether sulfate ammonium salt surfactant containing a mixture of alkyl groups.